Aluminum separation by sulfuric acid leaching-solvent extraction from Al-bearing LiFePO4/C powder for recycling of Fe/P

Recovery of battery-grade FePO4 from Al-bearing spent LiFePO4 batteries (LFPs) is important for both prevention of environmental pollution and recycling of resources for LFPs industries. The premise for FePO4 recovery from spent LFPs is the separation of Al, because Al readily co-precipitates with FePO4 and lowers the electrochemical performance of the regenerated LiFePO4. In this work, an efficient approach involving sulfuric acid leaching followed by solvent extraction was developed to separate Al from spent LiFePO4/C powder. Di-(2-ethylhexyl) phosphoric acid (D2EHPA) in sulfonated kerosene was used as the extractant. The results showed that 96.4% of aluminum was extracted while the loss of iron was only 1.1% under the optimal conditions. The mass fraction of Al in the iron phosphate obtained from the extraction raffinate was only 0.007%, meeting the standard for preparing battery-grade FePO4. The extracted Al can be easily stripped by diluted H2SO4 solution and the extractants can be reused. Additionally, slope analysis method, FTIR spectroscopy, and ESI-MS analysis revealed that the extraction of Al in D2EHPA can be ascribed to the ion exchange between hydrogen ion of -PO(OH) and Al3+. This work may provide an economically feasible method for the recycling of valuable components from spent Al-bearing LiFePO4/C powder.